Radio receiver



Jam 2l, 1947. F. w. FRINK RADIO RECEIVER Filed July 22, 1944 INVENTOR.

Patented Jan. 21, 1947 RADIO RECEIVER Frederick W. Frink, East Orange, N. J., assigner to Federal Telephone and Radio Corporation, New

York, N. Y.,

a corporation of Delaware Application uly 22, 1944, Serial N o. 546,119

Claims. (Cl. Z50-20) This invention relates to radio receivers and more particularly*to-receivers tunable over a very wide range of frequencies.

In the past, radio receivers tunable over relatively broad bands of frequency have been proposed. However, in general, these receivers are limited to a given bandwidth by the tuning characteristics of the input amplifier and the antenna systems. If broader band operation is required, it has generally been found necessary to provide additional receivers for these different bands which may be alternatively switched to a common reproducing unit.

It is an object of my invention to provide a relatively simple receiver circuit tunable over a very wide frequency band which may be considered as tunable over two contiguous frequency bands.

It is a further object of my invention to provide a super-heterodyne receiver circuit, wherein a single local oscillator serves to reducetlie frequencies of one given receiving band to a common intermediate frequency and to reduce the frequencies of another band to the same frequencies as those of the first given band and subsequently to the same intermediate frequency.,

According to a feature of my invention the beating oscillator which serves to reduce fre` quencies covering a normal given band from a first receiver unit to a common intermediate frequency is also used in a second mixer to reduce a second band of frequencies to the same frequencies as that of the first band named andthereafter to beat with these reduced signals to produce said common intermediate frequency. The rst receiver unit and the second mixer unit are made alternatively operative so that in effect the receiver may be continuously tuned over a band representing both of these given ranges.

A better understanding of my invention and the objects and features thereof may be had from the particular description of a preferred embodiment thereof made with reference to the accompanying drawing, the single figure of which` shows partly in schematic and partly in block circuit diagram a radio receiver unit incorporating the features of my invention. i.

At I is shown anantenna system operative over a lower frequency band coupled by means of a coupler unit 2 to the input circuit of a radio frequency amplifier 3. Radio frequency amplier 3 is coupled to a mixer circuit 4 wherein the incoming signals are mixed with the energy from beat oscillator 5 to reduce these incoming signals to a common intermediate frequency. The intermediate frequency signals in the output of mixer 4 are then applied to an intermediate frequencyY amplier 6 from whence they may be coupled over a line I `to a reproducing unit 8. Alternatively the signals from the intermediate frequency amplifier 6 may be applied over line 'I and a switch 9 to an indicator I0 if it is desired to determine the frequency of the received signals rather than to reproduce the signal energy.

A second antenna unit II operating over a higher frequency band is coupled over coupler unit I2'to a second mixer I3. Energy from beat frequency oscillator 5 is also applied to mixer i3 to reduce the signals incoming over antenna II and coupler I2 to the same range of frequencies as those received in amplifier 3. Second mixer I3 is coupled to the input circuit of mixer 4 so that these reduced signals may be further reduced to the common intermediate frequency after which they are amplified in intermediate frequency amplifier 6 and `reproduced in reproducing unit 8 or indicated on indicator I0.

A switching circuit I4 is provided to control a switching unit I5 which may be in the form of a trigger circuit, for selectively rendering amplifier 3 and mixer circuit I3 operative. A tuning control means I6 serves to simultaneously tune the inputs of amplifier 3, mixer 4, beating oscillator 5 and second mixer I3 and to control electronic switching circuit I4. Tuning control means l5 may be manual control means or may be a motor driven means to continuously scan the receiver over the frequency bands. Furthermore, if desired, tuning control means I6 may be mede selectively to operate either manually or under continuous motor control as desired, by arrangements well known in the art. Simultaneously with operation of electronic switch I4 an indicator control circuit I 4a is preferably provided to control indicator ID for the purpose of changing the indication depend-ing upon whether the frequency bandincomingover antenna I or II is effective at the time.

Turning more particularly to the circuit ar-V rangements of the system, amplifier 3 may comprise a vacuum tube amplifier I'I to the inputgrid of which is applied signals, over tuned circuit I8 consisting of transformer secondary I9 and tuning condenser 2l). The output energy from tube I 1 is supplied to mixer circuit 4, by

way of tuned input circuit 2|, provided with 'a` tunlngcondenser `22 cooperating with transformer primary 23. Condensers 20 and 22 are preferably simultaneously controlled. so that circuits I8 and 2| are both progressively tuned to the frequencies of the incoming carrier energy received on antenna system I. Energy from circuit 2l is then applied to the input grid circuit of mixer tube 24.

Beating oscillator i5 may comprisetube 25 oper.- ating as an oscillator at different lselected. frequencies by reason of the tuning of its tank circuit 26 consisting primarily of variable condenser 2'I and the output primary coil 28. APrimary coil 28 is coupled over secondary coil 29 and line Sil to the cathode lead of mixer .tube-24 so that the output energy from oscillator k5 is applied to mixer circuit d. As in known forms of super-heterodyne receivers, this beating v.frequency mixed with the incoming signals reduces the energy to a common, relatively fixed, intermediate frequency. In the output of tube 24 is provided tuned circuit 31| tuned to the fixed intermediate frequency. it will thus be ,seen that the sienalsiucorning overallteoria l are'reduced to a corriuiou intermediate rireduericy. Condenser 2l of oscillator 5 is simultaneously adjusted together with condenser `22 Vso that the ffleilllelldee of Oscillator 5 and timed .Circuit 2| are nroperlytracked to produce tiles-ingle :intern mediate `frequency.

Tire sis-nale iucorriririe vover antenna H :are of such arreoucney that they differ :from those iu- COlllIlg OVel zalltelllla by amounts equal t the frequency of beat frequency oscillator 5. These incoming signals are applied over a tuned circuit 3 2 .consisting primarily of transformer secondary 33 and tunable condenser y3d to the in.- put of second `lmixer tube 35. At the same time energy from beat oscillator is applied .over transformer 4secondary 3 6 and line 31 to the cathode of the second mixe-r tube 35 so that the incoming `energy over Aantenna I I .and the energy from beat frequency oscillator .5 will be mixed in tube 35. .Condenser 34 is suitably coupled n for simultaneoustuning with condenser 2'I.so that the reducedireduency, output .energy from tube t5 will cover-the sarde Y,f reduericyV rasee .as the inout enersyirrcoruius over .antenna l- These reduced frequency signals Afrom mixer tube 13.5 are there .applied over `line .ad to tuned input ,cire cuit .2i .oi flirter for .mi irre in tube 2.4 with the beat 1f .fluency .oscillat ris treni Oscillator .ii applied tli, .e.t.o vover transformer secondary .2e arid lead ed it will thus be that tire ire: duericies .of this second baud .reduced te the Saure ultimate rule ireduerlev as those of tire .iirst baud for reception and reproduction..

lr ampliiier .3 ,and second miser Itare .simultaneously effective, it is .clear that two separate frequencies .may simultaneously he received aud reduced to a common intermediate frequency, This v.rriieiit result confusion and interference in tire receiver or indicator. To prevent such an operation 1 provide a .switchirie arrangement which Amay be a known electronic switching circuit,`as indicated at I4. This switching circuit may be coupled over line 39 to the grid of tube 40 of ip-flopor triggered switching con-trol circuit L5. rvrihis circuit including tubes dll and 4I, is normally biased so that tube 4l! is inoperative while tube d! is conductive. When control energy from ld is applied to tube 4I, this tube ybecomes conductive and tube 4I non-conductive during the time this switching energy is applied. Switching circuit Id may be adjusted so that tubes r4I! and 4l are alternately conductive for the same 4 period of movement'of tuning control means I6. This period is preferably such that condensers 20 and 22 are swept through one complete control cycle of the incoming frequency band of antenna I. During the period when tube 4I is conductive, blocking energy is applied over potentiometer resistor 42 and control line 43 to the control grid of tube in vsecond mixer I3. Thus during this yperiod the receiver is yresponsive to energy incoming over antenna I and coupler2 but is blocked for energy incoming over antenna Ill vrand coupler I2. When the electronic switching circuit, however, applies potential to the grid -of tube .dal so that this tube becomes conductive, then a `blocking potential is applied over potentiometer dll and conductor 45 to the grid of tube Il of ampliiier k3 blocking this circuit and permitting energy incoming over antenna II and coupler I2 to be passed through the receiver cir'- cuit to the reproducing `or indicator units.

When Vthe circuit merely ier selectively receiving lcrie stat-ion over thee ire .double ircqueucy sweep, no special control .is necessary at reproducing .unit t. however. when it is .desired to .use the system for ysearching out Itransmitters and ydeterrriioiris ftiieiriredueucies; switch -9 may be closed so that :indicator -I'is in circuit. Indicator lll may be of any ldesired form :such as a pair of separate frequency indicating Vmeters or any other form `of `f reol-uency indicating V dev-ice. The position in the frequency vspectrum of the received signals may be made for example, along a sweep line timed for Aoperation with rotation of the tuning condensers. However, since the energies incoming over .antennas I and II yare reduced to the same frequency value, and the tuning condensers sweep through their t-u-ning cycles twice to cover the entire double band it is preferable to switch indicator lll simultaneously with the eiTect-ive switching .of xenergy from antennas I and I! so that ,the indications-will appear `,on definite separate scales. For .this pur.-

pose, arly iorrn of contr-ol switching unit, such as Shown at ltd may loe oper-ated under l.control of switching ,circuit I d simultaneously with the .opT

eration of the flip-.riep .circuiti so .that the proper scale will be indicated. Since Athenertieular form or indicator used is not :material to the operation of the system of this invention. details oi Ytrie circuit omitted.-

.lt Will be clear that iu accordance with my system, a iredueney band equivalent to two Separate normally received bands may be eiiectively received a continuously tuned receiver circuit.- Qther forms of circuit arrangements in.-

eoruoratius the broad. .ieatures of invention` will readily occur to those .skilled in .the art.

Whilev .I have described a Speciiic application of my invention to a receiver unit, it shouldbe distinctly understood that this is made merely by Way of illustration arid is riot intended asy any limitation ou invention .as set .forth in the obiectstlrereoi and the accompanying claims. l1 claim; I

in .a radio receiver tunable over different related .iirst .aud second frequency bands, a come mori rriiier circuit7 .a irst source of energy with in said first frequency band, second. source ci euersy Within said .second band, oscillator tunable over a baud oi `fredueucios, differing by a elven frequency from the. frequencies oi Said first band and.- differing by the frequencies oi said first band from the frequencies of s aid second band, mixer means for mixing energyfromsaid second source and energy from said oscillator to provide frequencies respectively equal to the frequencies of said first band, means for applying energy from said oscillator to said common mixer circuit and means for selectively applying energy from said first source band and energy from said mixer means to said common mixer circuit to provide output energy from said common mixer circuit at said given frequency over the entire range of said first and second bands.

2. The method of reducing energy received on different related first and second frequency bands to a common frequency by means of a single oscillator, comprising tuning said oscillator over a. frequency band equal to the difference frequency of said first and second bands and differing from the frequencies of said first band by said common frequency, mixing the energy output of said oscillator with the energies of said second band to reduce them to the same frequencies as said first band, and selectively mixing the energy output of Said oscillator with the energies of said first band and with the reduced frequency energies of said second band, to provide said common output frequency over said bands.

3. A radio receiver tunable for operation over a wide frequency band, comprising first means for receiving signals over one portion of said band, second means for receiving signals over the other portion of said band, an oscillator tunable over a given range of frequencies differing by a given intermediate frequency from the frequencies in said one portion of said band, and differing from the frequencies of said other portion of said band by amounts equal to the frequencies of said one portion of said band, means for mixing the energies from said oscillator and said other portion of said band to provide frequencies equivalent to the frequencies of said one portion of said band, a mixer circuit, means for supplying energy from said oscillator to said mixer circuit, and selective means for selectively applying energy from said first means and energy from said mixing means to said mixer circuit to produce output energy from said mixing circuit at said given intermediate frequency over said entire frequency band.

4. A receiver according to claim 3, further comprising means for continuously varying the tuning of said mixing means and said oscillator over their given ranges, and means for alternately rendering said first means and said mixing means effective.

5. A receiver according to claim 3 wherein said selective means comprises a trigger circuit for rendering the system operative to alternately pass signals from said rstrand second means, and electronic control means for controlling operation of said trigger circuit.

6. A receiver according to claim 3 further comprising a reproducing means for reproducing indications characteristic of the signals received over said band.

'7. A receiver according to claim 3 further comprising indicator means responsive to signals from said first and second receiver means coumeans controlled synchronously with said selective means for controlling said indicator means.

.pled to the output of said mixer circuit, and.

8. A radio receiver operative over a Wide frequency band, comprising a first receiver means tunable over a first frequency range, a first mixer circuit, a tunable heterodyne oscillator, means for applying signals from said first receiver means and the energy from said oscillator to said mixer circuit to produce a given intermediate frequency, a second receiver means responsive to frequencies in a second range contiguous to said rst range, a second mixer circuit, means for applying signals from said second receiver means and energy from said oscillator to said second mixer circuit to produce other intermediate frequencies corresponding in range to the frequencies of said first band, and means for applying energy from said second mixer circuit to said first mixer circuit simultaneously with energy from said oscillator to produce output energy of said given intermediate frequency, whereby signal energy over a band equal to said first and second ranges may be received.

9. In a radio receiver comprising an amplifier tunable over a first frequency range, a firs-t mixer circuit having an input tunable over said first frequency range coupled to said amplifier, an oscillator tunable over a given frequency range to produce a constant difference frequency between the 'oscillator energy and the energy of said first frequency range, and means for applying energy from said oscillator to said mixer circuit to produce an intermediate frequency at said constant difference frequency, an arrangement for effectively extending the range of said receiver ccmprising a second mixer circuit having an input tunable over a second range of frequencies differing from thev frequencies of said oscillator by the Ifrequencies of said first range, means for applying energy from said oscillator to said second mixer circuit to produce intermediate frequencies Within said first frequency range, means for applying said produced intermediate frequencies to the input circuit of said first mixer circuit, means for simultaneously tuning said mixers and said oscillator over their respective ranges, and means for renderingv said amplier and said second mixer alternately effective.

10. In a super-heterodyne receiver having an amplifier, a local oscillator, and a receiver mixer coupled to said amplifier and said local oscillator for reducing a given band of received frequencies to a given intermediate frequency, a further system for effectively extending the range of said receiver to an adjacent band of other frequencies comprising a reducing mixer circuit tunable over a second range of frequencies differing from the frequencies of said local oscillator by the frequencies of said given band, means coupling said oscillator to said reducing mixer to reduce the frequencies of said second range to the same values as those of said given range of frequencies, means coupling the output of said reducing mixer to the input of said receiver mixer, and means for selectively effectively applying the outputs of said amplifier and said reducing mixer to said receiver mixer, whereby the frequencies of said second range of frequencies are also reduced to said common intermediate frequency.

FREDERICK W. FRINK. 

